I'm fairly new to photography myself, so you are welcome to take this for what it's worth.

You should have a reflector throw more light onto her. That might offset the backlighting from the windows.

The few things I have been able to figure out and use are that an interesting photograph contains an interesting arrangement of....

lines and curves,
angles and perspective,
color and tone,
shadow and exposure,
position and attitude.

There are plenty of lines and curves in the room. Hers and elsewhere. Find an angle or different perspective to set the scene into an interesting pattern. You already know about the shadow and exposure part based on your comment about the backlight. Find an interesting position and get her to put on some sort of expression that will tell a story.

Was she surprised on the bed being silly? Or is the person that just walked into the room not who she was expecting?

Hmmmmm, hard to notice the "mistakes" with Rachel in the shot. after studying the image for some time the lighting didn't seem to be a major issue nor did the centering of the model given the symetry of the background. Perhaps a horizontal crop would have been better however the rest of the set may have prohibited that. After more than a few minutes, the one thing that did bother me, and the only thing, was how the drape laid in the image. The gold center is much narrower on the right than on the left. Still, only a very critical look identified that. This is a very pleasing image of a very beautiful woman. Thanks for sharing.
Jim